The present invention relates to a drive system for driving an electroluminescent (EL) display panel and, more particularly, to a power supply system in a driver circuit of an EL display panel.
Generally, a thin-film EL matrix display panel requires three voltage levels for achieving the display. More specifically, a logic circuit generally operates with a DC voltage of 5 to 15 volts. A driver circuit requires a second DC voltage of about 30 volts in order to develop a modulation voltage. The driver circuit further requires a third DC voltage of about 185 to 210 volts in order to develop a write pulse and a refresh pulse. In the conventional drive system of the thin-film EL matrix display panel, these three kinds of voltages are supplied from a power supply circuit to a driver circuit. This complicates the drive system of the thin-film EL matrix display panel, and disturbs the integration of the logic circuit with the driving pulse generation circuit.
Accordingly, an object of the present invention is to provide a novel drive system for a thin-film EL matrix display panel.
Another object of the present invention is to provide a drive system for an EL panel, which creates a refresh/write pulse voltage within the drive system, whereby the refresh/write pulse voltage is not required to be supplied from a power supply circuit to the drive system.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, only a logic drive voltage and a 1/4 V.sub.M voltage which has the 1/4 level of a modulation voltage V.sub.M are supplied from a power supply circuit to a drive system. The drive system includes a first voltage doubler circuit which introduces the 1/4 V.sub.M voltage and developes the modulation voltage in response to a timing signal. The drive system further includes a DC booster circuit such as a DC-DC converter for boosting the 1/4 V.sub.M voltage. An output voltage of the DC booster circuit is applied to a second voltage doubler circuit which generates the write pulse voltage and the refresh pulse voltage in response to the timing signal.